Why did Luke end Acts in the way that he did? The closing verses of Acts 28 serve, in part, to demonstrate Luke's point that the mission of the apostle Paul is a complete one. But in what sense is a description of Paul under house arrest for two years a conclusion to a largely itinerant ministry charted in the second half of Acts? To answer that question, we need to consider one other objective Luke has in concluding Acts in the way that he does. With the completion of Paul's ministry, a once-for-all apostolic foundation has been laid. 

To see how this is so, one must first appreciate the specific shape of Paul's ministry. It is, as Luke frequently reminds us, a ministry to Gentiles. This point surfaces in each of the three accounts of Paul's conversion and commission (9:15; 22:15,21; 26:16,27). It is a recurring feature of Paul's missionary campaigns in Acts. It is also the note on which Luke brings his account of Paul's labors to a close, "Therefore let it be known to you that this salvation of God has been sent to the Gentiles, and they will listen" (28:28). 

Paul's mission, then, is a Gentile mission. How does Luke represent this mission as brought to completion in Acts 28? To answer that question, we first need to consider Acts 1:8b, widely recognized as programmatic for the rest of Acts. In this verse, the risen but not yet ascended Jesus commissions the apostles to be his "witnesses in Jerusalem and in all Judea and Samaria and to the end of the earth." Luke proceeds to track the progression of the gospel from Jerusalem (Acts 1-7) to Judea and Samaria (Acts 8-12), and to the end of the earth (13-28). When Paul arrives at Rome, the gospel has reached "the end of the earth."  

What does this claim mean? What is "the end of the earth" and how has the gospel arrived there? Scholars debate the meaning of the phrase "the end of the earth." Some take it to refer to a geographical location, but differ as to what specific place(s) Luke has in mind. Others take the phrase to refer not to place but to people. "The end of the earth," then, refers to the Gentiles. 

One way to answer how Luke understands the phrase "the end of the earth" is to turn to the sole other instance of the phrase in Luke-Acts, Acts 13:47. There the phrase, appearing in a citation of Septuagint Isa 49:6, is parallel with "Gentiles." It is reasonable to conclude that the phrase "the end of the earth" at 1:8 also refers primarily to Gentiles. 

Luke is telling his readers that Paul's arrival and activities in Rome constitute the gospel's arrival at "the end of the earth." In other words, it is through Paul's Gentile mission that the gospel comes to "the end of the earth" and therefore brings the commission of Acts 1:8 to fulfillment. A closer look at Acts 13:47 helps us to see how Luke is making this claim. In this verse Luke appeals to Septuagint LXX Isa 49:6, one of the Isaianic Servant Songs. Strikingly, Paul makes application of this Servant Song to himself and to Barnabas. But hasn't Luke earlier told us that these Songs find their fulfillment in Jesus (see Luke 2:32)? He has, and Luke is not retracting that claim in Acts 13:47. It is through Paul that Christ brings salvation to "the end of the earth." Paul, in other words, is Christ's appointed instrument to bringing salvation to "the end of the earth." The completion of Paul's Gentile mission in Acts 28 represents the arrival of the gospel at "the end of the earth" and, therefore, the fulfillment of the commission of Acts 1:8. 

Many understand the commission of Acts 1:8 to be a standing commission for the church in every age. On this understanding of the commission, the apostles' gospel endeavors went a considerable distance in bringing that commission towards fulfillment. It is left, however, to the post-apostolic church and her missionary endeavors to complete what the apostles have begun. Paul may have achieved a provisional fulfillment of Acts 1:8, but it will be subsequent generations of the church who will exhaustively fulfill this commission. 

This common understanding of the commission of Acts 1:8 is mistaken. It is not a general commission for the church in every age. It is a commission to the apostles to carry the gospel, once and for all, across a redemptive-historical threshold. Now that Christ has died and been raised from the dead, the gospel must go not only to the Jew, but also to the Samaritan and to the Gentile. This movement of the gospel is non-episodic and epochal in character. Once the gospel has reached "the end of the earth" in Acts 28, Christ has laid through his apostles the once-for-all foundation upon which the church under the New Covenant will be built. 

How does Luke show us in Acts 28 that the gospel has crossed just such a redemptive-historical threshold? He does so in the pivotal citation of Isa 6:9-10 at Acts 28:26-27. When Paul's Jewish hearers reject the gospel he preaches (28:24-25), Paul invokes this text. He explains to those Jews who have refused the gospel that this refusal has occasioned the extension of the gospel to the Gentiles (28:28, cf. 13:46-47). Paul is not saying that the gospel will never again go to the Jew. After all, Paul welcomes "all who came to him" over the next two years (28:30). We have no reason to think that "all" did not include both Jews and Gentiles. 

Thus, Paul continued to preach to Jews and Gentiles after his initial encounter with his Jewish hearers in Rome. The significance of that encounter, as Paul explains it with reference to Isa 6:9-10, is epochal or redemptive-historical in nature. The gospel has definitively crossed an ethnic threshold and now goes to Jew and Gentile. Furthermore, it is Jewish unbelief that, in the purpose of God, has occasioned this epochal, once-for-all progression of the gospel to the Gentile. 

We are now in a position to summarize what Luke is saying in his conclusion to Acts. Paul's tenure in Rome renders his Gentile mission complete. Paul's Gentile mission is the way in which Christ ensured the fulfillment of the apostolic commission at Acts 1:8. What does it mean that this commission has been fulfilled? It means that the gospel has crossed a redemptive-historical threshold, decisively penetrating not only Jews and Samaritans, but also Gentiles. It means that a once-for-all foundation has been laid. 

This fact helps to explain the very last word of the Greek text of Acts, translated "without hindrance" (ESV). Although Paul is incarcerated and his immediate fate is uncertain to the reader, the Word that Paul preaches is unhindered. How could it be otherwise? Under the sovereign direction of the ascended Christ, the Word has made an epochal and irreversible advance. Whatever opposition the Word - and the servants of the Word - may face, the Word cannot be hindered from accomplishing all that God has purposed by it in the world. And that makes for a very happy and satisfying ending to the Acts of the Apostles.